Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$48.78	8.276%	$52.817	$52.82	$52.80	$52.80
Purchase #2	$64.75	12.403%	$72.7809	$72.78	$72.80	$72.80
Purchase #3	$149.77	11.358%	$166.7809	$166.78	$166.80	$166.80
Purchase #4	$154.38	9.506%	$169.0554	$169.06	$169.05	$169.10
Purchase #5	$65.32	9.103%	$71.2661	$71.27	$71.25	$71.30
Purchase #6	$62.81	6.376%	$66.8148	$66.81	$66.80	$66.80
Purchase #7	$88.88	4.456%	$92.8405	$92.84	$92.85	$92.80
7 purchase totals =	$634.69		$692.3556	$692.36	$692.35	$692.40